In recent years, hybrid vehicles have received attention as environmentally-friendly vehicles such as automobiles. A hybrid vehicle includes an internal combustion engine that is driven with gasoline and the like as fuel (hereinafter, referred to as engine) and an electric motor that is driven by electric power from a battery, as driving power sources.
As shown in FIG. 10, for such type of hybrid vehicle, the vehicle equipped with a driving system 300 formed with an engine 310, a driving unit 320, and a transmission 330 connected in series has been developed (for example, see Patent Document 1). The driving unit 320 includes an electric motor 321, a clutch 322, and a one-way clutch 323.
The electric motor 321 is disposed so as to rotate together with the transmission input shaft 331 of the transmission 330 as one unit. The clutch 322 is disposed between a crankshaft 311 of the engine 310 and the transmission input shaft 331 and changes a transmission state between the engine 310 and the electric motor 321 to a disengagement state and an engagement state. The one-way clutch 323 is disposed between the crankshaft 311 and the transmission input shaft 331 and transmits only power in a forward rotational direction from the engine 310 to the electric motor 321.
In the driving system 300, when the engine 310 is started, the clutch 322 is engaged, the electric motor 321 is driven, and the electric motor 321 cranks to start the engine 310 through the clutch 322. After the engine 310 starts, the clutch 322 is disengaged. Consequently, the output of the engine 310 is transmitted to the transmission 330 only through the one-way clutch 323.